1. Field of the Invention
The present invention relates to a basket-type grasping tool adapted for use in combination with an endoscope to endoscopically capture a foreign material or the like within a body cavity and remove the same therefrom.
2. Description of the Related Art
In general, a basket-type grasping tool has a basket section formed by at least three elastic wires that are bundled at both front and rear ends. The basket section is contracted by retracting the basket section into the tip end of a sheath. When the basket section is extracted from the tip end of the sheath, the basket section is expanded into a basket-like shape by its own elasticity.
The basket-type grasping tool is used such that the basket section is reciprocated in the axial direction of the sheath with respect to a foreign material or the like on the mucosa surface within a body cavity to endoscopically capture the foreign material inside the basket section.
Two types of grasping tools are available, one being designed so that elastic wires forming a basket section extend in parallel to the axial direction of a sheath, and the other (so-called "Dormia" basket-type endoscopic grasping tool disclosed in Japanese Patent Kokoku Publication No. 62-42617) being designed so that pairs of elastic wires forming a basket section are each twisted in opposite directions about the central axis of a sheath.
When a foreign material of a small size is to be captured using the former type of grasping tool, the foreign material is likely to pass through a gap between adjacent elastic wires to escape to the outside of the basket section. It is not rare that the foreign material escapes in this manner.
When the latter type of grasping tool is operated such that the basket section is reciprocated in the axial direction of the sheath, the elastic wires sometimes push the foreign material aside, and hence the foreign material does not enter the basket section.